Such a filter cartridge is known for instance from U.S. Pat. No. 2,630,227 and German Utility Model 7 017 889. There the two sieves rest loosely on or under the filter composition, so that shifting of the sieve from movement of the water and air is not precluded, which makes the retention action of the sieve inadequate in terms of preventing the granular filter composition from escaping.
Another disadvantage in the known filter cartridges is that venting is uncontrolled, so that the flow speed of the water is not controlled but instead proceeds unevenly and in fits and starts, so that the dwell time is varied and the dwell time required for optimal filtering is frequently not achieved.